I passed my theory test in 2008 and did a few lessons around then, but was fairly hamstrung by my own nerves and the fact that it's a completely different type of learning from anything I've done previously. I've been taking lessons solidly for the past two years, and made two attempts on the test this year. Despite the fact that I've been studying for one thing or another since I started secondary school, I can honestly say that no single qualification has cost me so much time and effort to get.
Of course, nothing else I've ever studied has been such a potentially lethal activity, so it's probably fair.
I may go and collapse on the couch for a while now.